White light LED and method to adjust the color output of same

Abstract

A white light LED having high color rendering indices and a correlated color temperature similar to that of an incandescent lamp. The LED has a semiconductor body formed of a semiconductor layer sequence capable of emitting electromagnetic radiation in a blue spectral range, the radiation exciting a yellow phosphor resulting in an intermediate blue-yellow light output whose chromaticity coordinates are transformed by a casting compound encompassing the semiconductor body and phosphor. A colored tint blended with epoxy resin forms the casting compound and filters the blue-yellow output, passing the red wavelength components of the blue-yellow output while attenuating the blue-yellow spectral wavelength, resulting in a balanced white output having a correlated color temperature, chromaticity coordinates, and color rendering indices similar to that of-an incandescent lamp output.

1 . A white light LED, comprising: 
 a semiconductor body formed of a semiconductor layer sequence emitting electromagnetic radiation in a blue spectral range when a forward bias is applied thereto;    a luminous material encompassing said semiconductor body, the luminous material being photoexcited by the electromagnetic radiation emission of the semiconductor body; and    a chromaticity coordinate-converting casting compound encompassing at least part of the semiconductor body and the luminous material;    wherein the LED device has a resultant white light output.    
   
   
       2 . The white light LED according to  claim 1 , wherein said casting compound comprises a transparent epoxy resin having a tint of predetermined color disposed in said resin.  
   
   
       3 . The white light LED according to  claim 2 , wherein said tint is a polycarbonate compatible tint, wherein said tint converts a wavelength falling within a blue wavelength range into a relatively longer wavelength.  
   
   
       4 . The white light LED according to  claim 1 , wherein said semiconductor body is a blue light emitting semiconductor body.  
   
   
       5 . The white light LED according to  claim 1 , wherein said luminous material is a phosphor exhibiting a yellow luminescence when photoexcited by the electromagnetic radiation emission of said semiconductor body.  
   
   
       6 . The white light LED according to  claim 1 , wherein said luminous material is a Ce-doped phosphor.  
   
   
       7 . The white light LED according to  claim 1 , wherein said blue light emitting semiconductor body and said luminous material emits an output wavelength in the blue-yellow spectrum.  
   
   
       8 . The white light LED according to  claim 1 , wherein said white light output has an approximate correlated color temperature (CCT) between 2,300 and 3,300 Kelvin.  
   
   
       9 . The white light LED according to  claim 1 , wherein said white light output has approximate chromaticity coordinates of X—0.466 and Y—0.442.  
   
   
       10 . The white light LED according to  claim 1 , wherein said white light output has a nominal color rendering index (CRI) of 85.  
   
   
       11 . A chromaticity coordinate-converting casting composition for die-level and mixed die white LEDs, the casting composition comprising: 
 a transparent epoxy resin; and    a polycarbonate compatible tint dispersed in said transparent epoxy resin, wherein the tint converts a wavelength falling within a blue wavelength range into a longer wavelength.    
   
   
       12 . The casting composition according to  claim 11 , wherein said tint is inert to said transparent epoxy resin and die chemicals.  
   
   
       13 . The casting composition according to  claim 11 , wherein said tint is chemically stabilized against ultraviolet light.  
   
   
       14 . The casting-composition according to  claim 11 , wherein said tint is heat-resistant.  
   
   
       15 . The casting composition according to  claim 11 , wherein said casting composition has chromaticity coordinates approximately equal to X—0.464, Y—0.350 and a color temperature of about 1900 Kelvin.  
   
   
       16 . The casting composition according to  claim 11 , wherein said tint and said epoxy resin have a dilution ration of approximately 50:1.  
   
   
       17 . The casting composition according to  claim 11 , wherein said tint has a formula range of L*65.77−a*41.27−b*62.57±5.  
   
   
       18 . The casting composition according to  claim 11 , wherein said tint shifts the output correlated color temperature from about 6,000 Kelvin to about 3,000 Kelvin.  
   
   
       19 . A method of adjusting the chromaticity coordinates and color rendering indices of a white LED, the method comprising the step of encapsulating said LED with a chromaticity coordinate altering compound.  
   
   
       20 . The method according to  claim 19 , further including the step of forming said chromaticity coordinate altering compound by diluting polycarbonate compatible tint, having a CIE-Lab formula range of L*65.77−a*41.27−b*62.57 plus or minus 5, with clear epoxy resin with a dilution ratio of 50:1.